Butyltins biomagnification from macroalgae to green sea urchin a field assessment.

код для вставки на сайт или в блог

ссылки на документ

APPLIED ORGANOMETALLIC CHEMISTRY
Appl. Organometal. Chem. 2003; 17: 759–766
Environment,
Published online in Wiley InterScience (www.interscience.wiley.com). DOI:10.1002/aoc.521
Biology and Toxicology
Butyltins biomagnification from macroalgae to green
sea urchin: a field assessment
Jean Mamelona and Émilien Pelletier*
Institut des Sciences de la Mer de Rimouski, Université du Québec à Rimouski, 310, Allée des Ursulines, Rimouski (Qc) G5L 3A1,
Canada
Received 28 April 2003; Accepted 11 June 2003
Biomagnification of butyltins (BTs) was examined in a simple food web including seawater, macroalgae (Alaria esculenta, Laminaria longicruris, Ulvaria obscura) and green urchin (Strongylocentrotus
droebachiensis). The study was conducted in shallow waters of the St Lawrence Estuary (Canada) adjacent to two areas potentially contaminated by BTs. Levels of tri- (TBT), di- (DBT) and mono-BT (MBT)
were determined in seawater, green urchin (including faecal matter after sampling) and macroalgae
surrounding the urchins at each sampling site. The concentrations of TBT in seawater from all stations
were relatively low (3–7 ngSn l−1 ), and both the TBT and the total BTs ( BT = MBT + DBT + TBT)
concentrations decreased with increase in distance from the BT sources. The concentrations of TBT
in algae were 0.35 ngSn g−1 dry weight (DW) in A. esculenta, 0.40 ngSn g−1 DW in L. longicruris
and 3.58 ngSn g−1 DW in U. obscura. Following their location, green urchins feeding mainly on
these algae accumulated BTs at levels ranging from 4 to 85 ngSn g−1 DW in gonads and from 35 to
334 ngSn g−1 DW in gut. The mean bioconcentration factor (BCF) calculated from seawater to algae
ranged from 17 in A. esculenta to 151 in U. obscura, whereas the biomagnification factor (BMF) from
algae to urchins ranged from 2 to 17 in gonads and from 10 to 67 in gut. The overall bioaccumulation
factor of TBT between seawater and internal organs of urchins reached an average value of 1.2 × 103 .
These results are the first to illustrate high BT BCFs and BMFs in human-edible macroalgae and
urchins sampled from northern coastal areas with a low TBT contamination level. Copyright  2003
John Wiley & Sons, Ltd.
KEYWORDS: tributyltin; green urchin; Strongylocentrotus droebachiensis; macroalgae; benthic ecosystem; St Lawrence Estuary
INTRODUCTION
Although tributyltin (TBT) has been pointed out as a major
pollutant in many coastal areas by numerous studies from
academics and governmental researchers,1,2 this biocide is
still in use in antifouling paints for large commercial vessels
and will be definitively banned from ship hulls only in 2008.3
TBT is often present at very low concentrations (<10 ng l−1 )
in coastal waters4 – 6 and could be erroneously considered
as harmless by the scientific community and regulators, as
*Correspondence to: Émilien Pelletier, Institut des Sciences de la
Mer de Rimouski, Université du Québec à Rimouski, 310, Allée des
Ursulines, Rimouski (Qc) G5L 3A1, Canada.
E-mail: emilien pelletier@uqar.qc.ca
Contract/grant sponsor: Natural Sciences and Engineering Research
Council of Canada.
Contract/grant sponsor: Canadian Research Chair in Marine
Ecotoxicology.
no obvious and alarming toxic effects can be observed or
related to TBT and its degradation products. However, subtle
effects on the immune and endocrine systems of invertebrates
have been clearly identified for very low concentrations
in seawater.7 – 9 Furthermore, the lipophilic nature of TBT
induces its rapid adsorption onto organic matter, and its
penetration in biological membranes.10 Plants and algae may
take up TBT from seawater, followed by its stepwise transfer
to primary consumers and upper predators, leading to its
accumulation within the food web.
In shallow waters and hard-bottomed benthic ecosystems,
macroalgae represent significant food sources for several
primary consumers, including urchins, gastropods, small
crustaceans and herbivorous fish. Little is known about
the accumulation of butyltins (BTs) by macroalgae and
their possible transfer to grazers. Available data from field
monitoring are limited to the BT levels in bladder wrack,
Copyright  2003 John Wiley & Sons, Ltd.
760
Environment, Biology and Toxicology
J. Mamelona and É. Pelletier
Fucus vesiculosis.11,12 BTs accumulation in macroalgae seems
to be species dependent, and levels in macroalgae are directly
related to levels found in the surrounding seawater.11 It could
be hypothesized that the exposure of algivorous organisms to
dietary BTs may lead to a biomagnification process that varies
between sites and which is strongly dependent upon the
bioconcentration factor (BCF) from seawater to macroalgae.
Green urchin, Strongylocentrotus droebachiensis, is an
intensive grazer that is widespread in the shallow waters
of North Atlantic coasts, including the estuary and the gulf
of the St Lawrence, where macroalgae and green urchins are
commercially harvested for food processing and potential
nutraceutical applications. A number of field surveys in the
last decade have shown that BT levels in sediment and benthic
organisms of the St Lawrence system were relatively low
and comparable to several other coastal sites in Canada.13 – 15
BTs are expected to be taken up by the green urchin from
seawater and macroalgae, as already observed for some other
inorganic and organic chemicals,16 – 18 but no field results have
been available up to now.
Our objective was to characterize the bioconcentration/biomagnification process of BTs in a simple food web
including seawater, macroalgae and green urchin using two
0
field sites where TBT is chronically present at relatively low
levels (<10 ng l−1 ). The study was conducted in shallow
waters along the south shore of the St Lawrence Estuary
adjacent to Les Méchins shipyard and Rimouski Harbor. The
sampling was conducted over a period corresponding to the
time of final growth of green urchin gonads and the beginning
of their commercial harvesting.
MATERIALS AND METHODS
Samples
In September 2002, seawater and biological samples were
collected at low tide from three stations around Les Méchins
shipyard (LM1, LM2, LM3) and two others near Rimouski
Harbor (RK1, RK2). An additional station located near the
shipyard (LM2a) was used for water sampling (Fig. 1). One
seawater sample per station was collected at 0.5 m below the
surface with 6 l polycarbonate bottles pre-rinsed with dilute
nitric acid (HNO3 ). Sea urchins were collected at the same
sites, cleaned of all algal fragments and separated into three
size classes: small (22.6 ± 2.2 mm in diameter, mean ± 1SD),
medium (35.8 ± 3.0 mm) and large (50.4 ± 4.4 mm). Three
macroalgae were collected at the same location as the seawater
0.5 km
LM1
Méchins Cove
LM2
LM2a
QUÉBEC
LM3
Sag
Riv uena
y
er
ce
ren
w
-La
St
Méchins River
Les Méchins
Shipyard
ary
tu
Es
Gaspé
Les Méchins
Rimouski
0
0.5 km
RK1
RK2
Rimouski Harbor
Rimouski City
Figure 1. Sampling stations in southern St Lawrence Estuary. TBT sources are expected to be from the shipyard at Les Méchins
and the inner harbour at Rimouski.
Copyright  2003 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2003; 17: 759–766
Environment, Biology and Toxicology
Biomagnification of butyltins
and urchins: Alaria esculenta, Laminaria longicruris and Ulvaria
obscura. Collected fronds (n = 3) were cleaned of all epiphytes
using seawater. All seawater and biological samples were
transported to the nearby ISMER marine station (Pointeau-Père, Qc, Canada), where the urchins were allowed to
evacuate faecal matter over 3 h. Faecal matter was collected
and separated from seawater by filtration. Urchins were
dissected, and gonads and gut were taken for chemical
analysis. Macroalgae, urchin organs and faecal matter were
freeze-dried for 96 h. Dry samples were ground and kept
frozen (−80 ◦ C) until BTs analysis.
of quantification of 0.25 ngSn l−1 (for a 6 l water sample) and
0.075 ngSn g−1 (for 0.25 g of biological dry sample).
Analysis of BT species
To obtain BMFs realistically related to the field diet of
sea urchins, the BTs in urchin algal food were calculated
as a weighted mean of BTs using the BTs concentration
in each alga and the relative proportion of each alga in
the green urchin diet according to the food preference of
S. droebachiensis. The preferred food composition (60% L.
longicruris, 30% A. esculenta, 10% U. obscura) was determined
from results previously obtained in our laboratory by feeding
urchins of various sizes ad libitum with a mix of all three algae
(Mamelona, unpublished data).
The analytical procedures for BTs in seawater and biological
samples were based on a previously described method.19,20
Seawater was transferred immediately upon sampling in
3 × 2 l glass flasks and acidified with 3 M HNO3 to reach
pH 5.5. BTs were ethylated by vigorously shaking samples
for 5 min with 0.5 ml of 4% sodium tetraethyl borate
(NaBEt4 ). After ethylation, BT were extracted with 10 ml of
isooctane/pentane (1 : 4) by thoroughly shaking for 10 min.
Tetrapentyltin (TePSn) was added as an internal standard.
For analysis of BTs in biological samples, 0.1–0.5 g of pooled
dry matter (n = 3–4) was digested for 60 min at 55 ◦ C using
5 ml of tetramethylammonium hydroxide. The mixture was
thereafter acidified with 25 ml of acetate buffer (pH 4.1). BTs
were extracted with 2 ml of hexane. After adding internal
standard (TePSn) the BTs were ethylated twice by shaking for
15 min with 0.6 ml of NaBEt4 . The organic layer was removed
and 1 ml of this extract was dried with Na2 SO4 and cleaned by
passing through 5% silica gel (5 cm × 0.8 cm ID) and eluted
with additional 5 ml of hexane. The cleaned mixture was
evaporated under nitrogen flow to 0.2 ml.
Samples extracts were analysed for BTs using gas
chromatography coupled to a mass spectrometer (MS:
TraceGC 2000/PolarisQ, ThermoFinnigan, Mississauga ON,
Canada). Chromatographic separation was performed on
a 30 m × 0.25 mm ID capillary column with 0.25 µm film
thickness coating (Rtx-5 MS, Restek Co., UK). The gas carrier
was helium (1 ml min−1 ). The injection temperature was
increased from 100 to 250 ◦ C at a rate of 10 ◦ C s−1 and the oven
was programmed from 80 to 250 ◦ C at a rate of 12 ◦ C min−1 .
The identification of chromatographic peaks was performed
in segmented scan mode with five typical ion groups of BT
compounds. Standard curves for the quantification of monoBT (MBT), di-BT (DBT), and TBT ethyl derivatives were
prepared following the above the procedure by replacing
biological samples with solutions of known concentrations of
BTs in dry ethanol. The recovery of BT species from mussel
standard CRM 477 (n = 6) was 92 ± 11% for MBT, 74 ± 11%
for DBT and 79 ± 12% for TBT. The concentrations of BTs
were not corrected for recovery. The correlation coefficients
r2 between MS responses and standard concentrations were
>0.99 for MBT, DBT and TBT. The detection limit of MS for
BT species was 1.5 pg of tin per injection (1 µl), giving a limit
Copyright  2003 John Wiley & Sons, Ltd.
Data analysis
The BCF and the biomagnification factor (BMF) were
calculated as follows:
BCF =
BTs in tissue (ngSn g−1 wet weight (WW))
BTs in seawater (ngSn ml−1 )
(1)
BMF =
BTs in tissue (ngSn g−1 dry weight (DW))
BTs in algal food (ngSn g−1 DW)
(2)
RESULTS
BTs in seawater
BT compounds were detected in all seawater samples
collected from six stations (Table 1). Total BT concentrations
( BT = MBT + DBT + TBT) in water varied from 4.7
to 13.8 ngSn l−1 . Total BTs and individual BT species
concentrations in seawater were about two times higher
at Les Méchins (LM) than at Rimouski (RK) stations. The
highest levels were found close to TBT potential sources,
and both total BT and TBT concentrations in seawater
decreased slightly with increasing distance from the sources.
A comparable distribution of BT species was observed for
both locations. TBT was generally the dominant species except
for seawater collected from LM1, where the MBT level was
up to two times higher than TBT. The TBT/DBT ratio was up
to 7.4 for seawater sampled close to the shipyard (LM2a), and
Table 1. Distribution of BTs species (ngSn l−1 ) in seawater
collected from six stations in the southern St Lawrence Estuary
in September 2002
Station
MBT
DBT
TBT
BTs
TBT/DBT
LM1
LM2
LM2a
LM3
RK1
RK2
7.5
3.1
5.4
3.2
1.6
1.3
1.0
1.5
1.0
1.4
0.7
0.6
3.8
5.4
7.4
5.1
3.3
2.8
12.3
10.0
13.8
9.7
5.6
4.7
3.8
3.6
7.4
3.6
4.6
4.7
Appl. Organometal. Chem. 2003; 17: 759–766
761
762
Environment, Biology and Toxicology
J. Mamelona and É. Pelletier
Table 2. Concentration and distribution of BTs species in
macroalgae collected from four stations in the southern St
Lawrence Estuary in September 2002. Values are obtained
from pooled samples (n = 3); ql: below quantification limit; nd:
not determined because Alaria was absent in LM2
Station
Alga
BT concentration (ngSn g−1 DW)
MBT
DBT
TBT
BTs
LM1
A. esculenta
L. longicruris
U. obscura
A. esculenta
L. longicruris
U. obscura
A. esculenta
L. longicruris
U. obscura
A. esculenta
L. longicruris
U. obscura
2.59
1.56
0.94
nd
1.24
3.76
ql
2.25
1.53
ql
6.17
0.77
LM2
LM3
RK2
ql
ql
0.48
nd
ql
1.92
ql
ql
0.78
ql
ql
ql
0.49
0.43
0.87
nd
0.62
6.52
0.18
0.33
2.35
0.39
0.23
4.59
3.08
1.99
2.29
nd
1.86
12.20
0.18
2.58
4.66
0.39
6.40
5.36
this ratio decreased with increasing distance from the sources
for Les Méchins stations (Table 1).
BTs in macroalgae and in faecal matter
BT compounds were detected in all three algal species
collected from the four sites (Table 2). The concentrations
of total BTs varied from 0.18 to 12.2 ngSn g−1 DW depending
on the particular alga species. The distribution of BTs
also varied with the alga. It decreased in the sequence
TBT > MBT > DBT in Ulvaria. DBT was detected only at
trace levels in Ulvaria collected from RK2. TBT was generally
at a low level in Alaria and Laminaria. MBT was the dominant
species of BT in Laminaria, with a mean concentration five
times higher than TBT. This was the same for Alaria in
LM1. DBT was not detected or was at trace levels in most
samples. Although the highest concentrations of BT species
and total BTs were found in the inner part of the shipyard
(LM2 and LM2a), there is no clear relationship between the
concentration of BTs in seawater and concentrations found in
macroalgae. For example, total BTs and TBT concentrations
were higher in seawater from LM3 than RK2, whereas the
inverse relationship was found for Ulvaria from these two
sites.
There was a significant bioconcentration (BCFs > 1) of BT
compounds from surrounding seawater to macroalgae. BCFs
ranged from 5 to 543 and 3 to 244 for individual BT species
and total BTs respectively (Table 3). Variation of BCF between
species was notably found for TBT. When considering all
stations and sites, BCFs of TBT were strikingly higher in
Ulvaria than in Alaria and Laminaria (ANOVA, F1,2 = 5.419,
p = 0.033; SNK, p < 0.05). On average, there was over 150fold more TBT in Ulvaria than in the surrounding water,
whereas this factor averaged 10 in Alaria and Laminaria.
Copyright  2003 John Wiley & Sons, Ltd.
Table 3. BCFs of BTs species by macroalgae collected from
four stations in the southern St Lawrence Estuary in September
2002; nd: not determined because BT concentration was below
the quantification limit in macroalgae
Station
LM1
LM2
LM3
RK2
BCF [(ng g−1 WW)/(ng ml−1 )]
MBT
DBT
TBT
BTs
Alga
A. esculenta
L. longicruris
U. obscura
A. esculenta
L. longicruris
U. obscura
A. esculenta
L. longicruris
U. obscura
A. esculenta
L. longicruris
U. obscura
54.8
23.5
25.7
nd
44.8
241.6
nd
78.4
93.1
nd
543.1
120.8
nd
nd
93.1
nd
nd
261.4
nd
nd
112.9
nd
nd
nd
20.9
12.3
45.5
nd
12.3
239.6
11.3
7.8
91.1
4.8
9.0
324.8
40.3
17.9
37.6
nd
21.3
243.6
6.4
30.2
95
3.2
154.5
227.7
BTs were found in faecal matter of urchins collected from
the five stations (Fig. 2). BT concentration varied depending
on both urchin size and sampling station. The highest total
BT concentration in faecal matter was up to 5.5 ngSn g−1
and observed in large urchins collected close to the most
contaminated station (LM2). However, the spatial variation of
BTs in faecal matter did not follow the BTs’ spatial variation in
macroalgae. For example, the total BT concentration in faecal
matter of medium urchins collected from LM3 was higher
than from LM1, whereas the inverse relationship was found
in Laminaria and Ulvaria. The composition of BTs in faecal
matter also varied depending on urchin size and sampling
station. Although, MBT and TBT were omnipresent, DBT
was barely present or not detected, as already observed in
macroalgae.
BTs accumulation in urchins
BTs were found in gonads and gut of all urchins collected from
the five sites (Table 4). BT concentrations were significantly
higher in gut than gonads for TBT alone (t0.05,24 = 3.424,
p = 0.002), and also total BTs (t0.05,24 = 2.688, p = 0.013). TBT
concentrations in urchins from Les Méchins were comparable
to those from RK stations in both gonads (t0.05,11 = 0.286,
p = 0.780) and gut (t0.05,11 = 0.183, p = 0.858). Similarly, total
BT concentrations in urchin organs were not significantly
different between sampling sites (t0.05,11 = 0.285, p = 0.781 for
gonads and t0.05,11 = 0.484, p = 0.638 for gut).
Total BT concentration in gut decreased in the order
LM2 > LM3 > LM1 and RK1 > RK2. The composition of
BTs decreased in the sequence TBT > MBT > DBT except
for LM1, where MBT in gut was higher than TBT (Table 4).
At the three LM stations, the total BT concentration in gut
was higher for large urchins than smaller ones. However, the
total BT concentration in gut of individuals collected from the
Appl. Organometal. Chem. 2003; 17: 759–766
Environment, Biology and Toxicology
6
Small urchins
5
4
Biomagnification of butyltins
Table 4. Concentration and distribution of BTs species in
three size classes of urchin collected from five stations in the
southern St Lawrence Estuary in September 2002. Values are
means (n = 2–4) obtained from each urchin size and organ;
ql: below quantification limit
3
BT concentration
(ngSn g−1 DW)
2
1
nd
Butyltin concentration (ng Sn. g-1 d.w.)
0
nd
nd
nd
Station
Size class
Organ
MBT
DBT
TBT
BTs
LM1
Large
Gonad 11.16
Gut
35.41
Gonad 42.94
Gut
28.64
Gonad 13.35
Gut
25.98
Gonad 48.69
Gut
174.48
Gonad 31.33
Gut
88.51
Gonad
2.72
Gut
26.07
Gonad
0.57
Gut
10.46
Gonad
0.38
Gut
15.02
Gonad 51.74
Gut
36.64
Gonad
2.11
Gut
24.13
Gonad
3.52
Gut
29.49
Gonad
3.32
Gut
14.77
Gonad
2.08
Gut
19.49
0.13
0.80
0.38
0.93
0.27
1.59
13.21
35.39
2.17
17.12
0.40
6.65
0.20
4.79
ql
4.61
6.81
5.09
0.59
5.44
0.50
9.88
0.11
3.74
0.34
4.58
5.22
17.03
7.99
18.40
4.12
7.44
23.39
123.94
26.75
102.65
12.06
48.79
11.65
42.65
3.84
27.08
13.68
47.21
10.95
36.58
22.95
117.97
8.91
25.79
9.28
36.17
16.51
53.24
51.31
47.97
17.74
35.01
85.29
333.81
60.25
208.27
15.18
81.51
12.42
57.90
4.27
46.71
72.23
88.94
13.65
66.15
26.97
157.34
12.34
44.30
16.70
60.23
6
Medium
Medium urchins
5
Small
4
LM2
Large
3
Medium
2
LM3
1
0
Large
Medium
6
4
Small
Large urchins
TBT
DBT
MBT
5
RK1
Large
3
Medium
2
Small
1
nd
RK2
Large
K2
Medium
R
K1
R
3
LM
2
LM
LM
1
0
Figure 2. Concentration and distribution of BTs species in
urchin faecal matter collected from five stations in the southern
St Lawrence Estuary in September 2002; nd: not determined
because faecal matter was not available.
two RK stations was in the order: small > large > medium
urchins. The total BT concentration in gonads decreased in
the order LM2 > LM1 > LM3 and RK1 > RK2. MBT was the
dominant species of BT in gonads of urchins collected from
LM1 and LM2, whereas TBT was first for those from LM3,
RK1 and RK2, except for large urchins from RK1. The total
BT concentration was usually higher in gonads of larger
urchins.
Table 5. Mean concentration of BTs species in a typical green
urchin algal meal based on the food preference of the urchins
and used to calculate BMFs; nd: not determined because no
DBT value available in the three macroalgae at that station
Station
BT concentration (ngSn g−1 DW)
MBT
DBT
TBT
BTs
LM1
LM2
LM3
RK2
1.81
1.99
2.04
3.78
0.05
0.19
0.08
nd
0.49
2.39
0.55
0.65
2.35
4.96
2.13
4.43
BMFs in urchins
Following the method previously described, the concentrations of BT species in a typical urchin meal were calculated
for four stations with available data and are summarized
in Table 5. The mean concentrations are slightly above the
Copyright  2003 John Wiley & Sons, Ltd.
individual Alaria and Laminaria values but are clearly below
Ulvaria, which has a low contribution to the diet.
Significant BMFs (>1) of BTs in gonads and gut were found
for all urchins and ranged from 2 to 22 in gonads and 10 to
Appl. Organometal. Chem. 2003; 17: 759–766
763
764
Environment, Biology and Toxicology
J. Mamelona and É. Pelletier
Table 6. BMFs of BTs species between algal food and urchin
internal organs; nd: not determined because no DBT value
available in algal food
Station
Size class
Organ
BMF [(ng g−1 DW)/
(ng g−1 DW)]
MBT DBT TBT
BTs
LM1
Large
Gonad
Gut
Gonad
Gut
Gonad
Gut
Gonad
Gut
Gonad
Gut
Gonad
Gut
Gonad
Gut
Gonad
Gut
Gonad
Gut
Gonad
Gut
6.2
19.6
23.7
15.8
7.4
14.4
24.5
87.7
15.7
44.5
1.3
12.8
0.3
5.1
0.2
7.4
0.9
3.9
0.6
5.2
Medium
Small
LM2
Large
Medium
LM3
Large
Medium
Small
RK2
Large
Medium
2.6
16.0
7.6
18.6
5.4
31.8
69.5
186.3
11.4
90.1
5.0
83.1
2.5
59.9
nd
58.1
nd
nd
nd
nd
10.7
34.8
16.3
37.6
8.4
15.2
9.8
51.9
11.2
42.9
21.9
88.7
21.2
77.6
7.0
49.2
13.7
39.7
14.3
55.6
7.0
22.7
21.8
20.4
7.6
14.9
17.2
67.3
12.1
42.0
7.1
38.3
5.8
27.2
2.0
21.9
2.8
10.0
3.8
13.6
67 in gut (Table 6). BMF of TBT alone varied from 7 to 21 in
gonads and from 15 to 89 in gut. The BMFs of total BTs in
gut were the highest at the most contaminated station (LM2),
although the BMFs of TBT in gut were higher at LM3 than
at LM2. In general, the BMFs of both total BTs and TBT in
gut were higher in large and medium urchins than in small
urchins. Both the total BTs and TBT BMFs in gonads did
not show a clear correlation with either sampling station or
urchin size (Table 6).
DISCUSSION
Once released in seawater, TBT is rapidly adsorbed onto
suspended particulate matter, macroalgae, and organiccoated surfaces, and eventually degraded to DBT and MBT.
The TBT half-life in seawater is generally estimated in the
range of a few days to a few weeks.2,21,22 The relatively high
proportion of TBT among BT derivatives found in the present
study suggests that its low but fresh input in the waters
adjacent to our two sampling areas most probably comes from
shipyard and boating activities. This study first reported TBT
seawater level in the St Lawrence Estuary. TBT concentrations
in all stations (3–7 ng l−1 ) were far below those reported in
some highly contaminated coastal shallow waters (up to
630 ng l−1 ).23 – 25 Though considered quite low, the observed
Copyright  2003 John Wiley & Sons, Ltd.
TBT water concentrations could be deleterious to the health
of marine ecosystems because they exceed the concentration
(∼1 ng l−1 ) that causes chronic effects to the reproduction
of several organisms2,7,10 and impairs their immune system.8
Furthermore, these seawater TBT levels were sufficiently high
to induce a stepwise bioaccumulation within the food web.
The only previous TBT levels reported in macroalgae were
for the bladder wrack, F. vesiculosis,11,12 a species usually
avoided by several macrobenthic grazers because of its high
chemical defence against herbivory.26 The TBT level was as
high as 42–97 ngSn g−1 (WW) in algae from the German
North Sea,11 whereas it was 2–4 ngSn g−1 in the same species
collected along Danish coasts.12 The calculated BCF was up
to 2 × 104 for F. vesiculosis collected from the North Sea. We
first report the TBT level and BCFs in three macroalgae,
which are not only dainty food sources for several herbivores
living in benthic hard-bottomed ecosystems but are also used
by man as seafood or in nutraceutical and pharmaceutical
applications.27 The observed BCFs were far lower than those
reported for bladder wrack in the North Sea, although
seawater TBT level (up to 4 ngSn l−1 ) was in the same range
as the one reported in our own stations. At our sampling
sites, the BCFs of TBT ranged from a low 5 in Alaria to a high
325 in Ulvaria collected at the same station, indicating a huge
range of values for the macroalga species and the location. As
a major source of organic carbon used by nearshore benthic
ecosystems, macroalgae may therefore represent significant
initial sources of TBT for the rest of the food web.
Sea lettuce U. obscura accumulated TBT at a much higher
level than the two brown algae. This significant difference in
TBT accumulation and BCFs between macroalgae might be
related to the difference in biochemical and physical nature
of these algae. The thin sheet-like thallus of Ulvaria probably
increases its relative adsorption surface28 compared with the
two brown algae. Moreover, this alga is formed by only two
cell layers and contains much more fat (7% DW) than the two
brown algae (4% DW), which probably favours rapid TBT
incorporation and scavenging in algal components.
The presence of BT species in the daily diet of urchins is
clear from the presence of BTs in their faecal matter at a level
that is often higher than in some individual algae collected
at the same location. This apparent discrepancy is linked to
the specific diet of urchins in the hours before their sampling,
as they grazed an unknown proportion of the three algae
collected or even of algal species not sampled but which
are also part of their diet.29 The use of a weighted mean
of BTs with a standardized meal based on food preference
circumvents the problem of calculating the BMF with only
one alga species.
A biomagnification of TBT more than 20 times higher than
in algal food sources has been observed in gonads and gut
of urchins. Although a direct bioaccumulation of BTs from
seawater into sea urchin organs cannot be totally excluded,
it is reasonable to assume that food is by far the main source
of BTs for internal organs such as gonads and gut as they are
energy storage tissues in urchins. Our BMF data are the first
Appl. Organometal. Chem. 2003; 17: 759–766
Environment, Biology and Toxicology
to be reported for BTs in a macrophyte grazer. The observed
values are much higher than the BMFs of TBT previously
reported (0.04–7.5) in shellfish and fish from laboratory
experiments,30 – 34 and from field studies at the upper end
of the food chain, such as in sea bird or mammals.35 – 40 A
comparison with an other echinoderm species (Leptasterias
polaris) living in the same area as the green urchin showed
a much lower BMF in gonads (BMF = 1.3, n = 9 sites) and
its digestive tracts (BMF = 1.5) (recalculated from Pelletier
and Normandeau13 ). It seems that sea star L. polaris has a
much better capacity to biodegrade and eliminate BT species
than sea urchin. Starting from a low 4.63 ngSn l−1 in seawater
(mean for all stations), the TBT concentration reached an
average of 5620 ngSn kg−1 WW (mean value calculated for
all stations and urchin sizes) in urchin soft tissues (gonads
and gut pooled together and using a conversion factor of
0.18 from DW to WW). The resulting effect corresponds to an
overall bioaccumulation factor (BAF) of approximately 1214.
The BAF reaches 1950 when only gut concentrations are used
in the calculation.
We compared our data with data previously reported by
Takahashi et al.23 for the related species Strongylocentrotus
intermedius. This shows that the total BTs and TBT mean
concentrations in S. droebachiensis soft tissues from the St
Lawrence Estuary are respectively four and six times lower
than the levels in S. intermedius living in shallow waters,
with total BTs (17 ng l−1 ) and TBT (4 ng l−1 ) comparable
to those found in the present study (5–14 ng l−1 and
3–7 ng l−1 , respectively), thus confirming the high retention
and apparently low excretion of BTs by the Strongylocentrotus
species. Finally, it should be mentioned that we found more
BTs in gut than in gonads, regardless of sampling stations
and urchin sizes. This is explained by the fact that gut was in
direct contact with dietary BTs and its high contains in total
lipids (23% DW) compared with gonads (16% DW).
CONCLUSION
This paper presents the first detailed field results on the
transfer of dissolved BT species to macroalgae and to the
grazer S. droebachiensis. Although these are low levels of
TBT present in seawater for both sites sampled, the average
BCF in macroalgae reached 71 and the BMF for green
urchin was in the order of 31. Significant differences in the
capacity of macroalgal species to adsorb BTs are observed,
especially of Ulvaria, which seems particularly sensitive to
bioaccumulation of BTs. TBT was found to be about 1200
times more concentrated in sea urchin soft tissues than in
the surrounding seawater. These results point out the risk
of BTs contamination of edible macroalgae and the highly
appreciated green urchin in an estuarine environment with
a quite low contamination level by BT species. These results
also point out the need for the rapid enforcement of a world
ban of TBT paints.
Copyright  2003 John Wiley & Sons, Ltd.
Biomagnification of butyltins
Acknowledgements
This research was supported by the Natural Sciences and Engineering
Research Council of Canada and the Canadian Research Chair
in Marine Ecotoxicology. J.M. was awarded a fellowship by
the Canadian Program of student fellowship to French-speaking
countries.
REFERENCES
1. Evans SM. Mar. Pollut. Bull. 1999; 38: 629.
2. Omae I. Appl. Organometal. Chem. 2003; 17: 81.
3. IMO. Focus on IMO. Antifouling systems: moving toward
the non-toxic solution. Report of International Maritime
Organization, UK, April 1999.
4. Michel P, Averty B. Mar. Pollut. Bull. 1999; 38: 268.
5. Thomas KV, Fileman TW, Readman JW, Waldock MJ. Mar.
Pollut. Bull. 2001; 42: 677.
6. Gui-bin J, Qun-fang Z, Ji-yan L, Di-jing W. Environ. Pollut. 2001;
115: 81.
7. Alzieu C. Ecotoxicology 2000; 9: 71.
8. Saint-Jean SD, Pelletier E, Courtenay SC. Mar. Ecol. Prog. Ser.
2002; 236: 155.
9. Mercier A, Pelletier E, Hamel JF. Aquat. Toxicol. 1994; 28: 259.
10. Meador JP. Rev. Environ. Contam. Toxicol. 2000; 166: 1.
11. Shawky S, Emons H. Chemosphere 1998; 36: 523.
12. Strand J, Jacobsen JA. Forekomst af organiske tinforbindelser i planter
og dyr fra danske farvande: akkumulering og fØdekæderelationer.
MiljØ-og Energiministeriet Danmarks MiljØundersØgelser,
2000; Arbejdsrapport fra DMU nr. 135.
13. Pelletier E, Normandeau C. Environ. Technol. 1997; 18: 1203.
14. Saint-Louis R, Gobeil C, Pelletier E. Environ. Technol. 1997; 18:
1209.
15. Saint-Jean SD, Courtenay SC, Pelletier E, Saint-Louis R. Environ.
Technol. 1999; 20: 1203.
16. Warnau M, Teyssié JL, Fowler SW. Mar. Ecol. Prog. Ser. 1995; 126:
305.
17. Warnau M, Ledent G, Temara A, Jangoux M, Dubois P. Mar. Ecol.
Prog. Ser. 1995; 116: 117.
18. Schweitzer LE, Bay SM, Suffet IH. Environ. Toxicol. Chem. 2000;
19: 1919.
19. Michel P, Averty B. Environ. Sci. Technol. 1999; 33: 2524.
20. Chau YK, Yang F, Brown M. Anal. Chim. Acta 1997; 338: 51.
21. Watanabe N, Sakai S, Takatsuki H. Water Sci. Technol. 1992; 25:
117.
22. Stewart C, de Mora SJ. Environ. Technol. 1990; 11: 565.
23. Takahashi S, Tanabe S, Takeuchi I, Miyazaki N. Arch. Environ.
Contam. Toxicol. 1999; 37: 50.
24. Gomez-Ariza JL, Giraldez I, Morales E. Water Air Soil Pollut. 2001;
126: 253.
25. Nemanič TM, Leskovšek H, Horvat M, Vrišer B, Bolje A. J.
Environ. Monit. 2002; 4: 426.
26. Targett NM, Arnold TM. J. Phycol. 1998; 34: 195.
27. Zemke-White WL, Ohno M. J. Appl. Phycol. 1999; 11: 369.
28. Lobban CS, Harrison PJ. Seaweed Ecology and Physiology.
Cambridge University Press: New York, 1994.
29. Himmelman JH, Nédélec H. Can. J. Fish. Aquat. Sci. 1990; 47: 1011.
30. Yamada H, Tateishi M, Takayanagi K. Environ. Toxicol. Chem.
1994; 13: 1415.
31. Tsuda T, Aoki S, Kojima M, Harada H. Comp. Biochem. Physiol. C
1991; 99: 69.
32. Laughlin RB, French W, Guard HE. Environ. Sci. Technol. 1986;
20: 884.
33. Bryan GW, Gibbs PE, Hummerstone LG, Burt GR. Mar. Environ.
Res. 1989; 28: 241.
Appl. Organometal. Chem. 2003; 17: 759–766
765
766
J. Mamelona and É. Pelletier
34. Stickle WB, Sharp-Dahl JL, Rice SD, Short JW. J. Exp. Mar. Biol.
Ecol. 1990; 143: 165.
35. Iwata H, Tanabe S, Mizuno T, Tatsukawa R. Environ. Sci. Technol.
1995; 29: 2959.
36. Guruge KS, Tanabe S, Iwata H, Tatsukawa R, Yamagishi S. Arch.
Environ. Contam. Toxicol. 1996; 31: 210.
37. Kim GB, Tanabe S, Tatsukawa R, Loughlin TR, Shimazaki K.
Environ. Toxicol. Chem. 1996; 15: 2043.
Copyright  2003 John Wiley & Sons, Ltd.
Environment, Biology and Toxicology
38. Guruge KS, Tanabe S, Iwata H, Tatsukawa R, Amano M,
Miyazaki N, Tanaka H. Environ. Sci. Technol. 1996; 30: 2620.
39. Kannan K, Senthilkumar K, Loganathan BG, Takahashi S,
Odell DK, Tanabe S. Environ. Sci. Technol. 1997; 31: 296.
40. Kannan K, Senthilkumar K, Sinha R. Appl. Organometal. Chem.
1997; 11: 223.
Appl. Organometal. Chem. 2003; 17: 759–766